Processes for producing low nitrogen metallic chromium and chromium-containing alloys and the resulting products

a technology of metallic chromium and alloys, which is applied in the field of metalothermic processes for producing low nitrogen metallic chromium and its alloys, can solve the problems of limiting the number of cycles the part will withstand during its service life, reducing the service life and removing the nitrogen and/or the nitrogen-containing precipitates after the reduction of the metal or metal alloy is an extremely difficult and expensive task, and the process is expensive and slow

Active Publication Date: 2018-08-07
CIA BRASILEIRA DE METALURGIA E MINERCAO
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  • Summary
  • Abstract
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  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This method effectively reduces nitrogen content in metallic chromium and chromium-containing alloys to below 10 ppm, overcoming the challenges of nitrogen absorption and ensuring low nitrogen levels in the final product, which is crucial for extending the lifespan of rotating metal parts in aircraft engines and oil and gas equipment.

Problems solved by technology

That, in turn, limits the number of cycles the part will withstand during its service life.
It is known that removing the nitrogen and / or the nitrogen-containing precipitates after the reduction of a metal or metal alloy is an extremely difficult and expensive task.
There is a well known process for producing low nitrogen alloys called electron beam melting; it is very expensive and extremely slow when compared to a metallothermic reduction process and therefore, impractical from a commercial point of view.

Method used

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Examples

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examples

[0031]The following examples were conducted to establish the effectiveness of the embodiments of the present invention in obtaining low nitrogen chromium and chromium alloys.

[0032]In the following examples, an aluminothermic reduction reaction was effected in the manner disclosed below. Table 1 summarizes the composition of the materials charged to the reactor:

[0033]

Example 1Example 2Nb17—Cr68—Ni15Nb17—Cr68—Ni15Target Alloy(g)(%)(g)(%)Nb2O526710.679510.6Cr2O3109343.4324943.3Ni1656.54906.5KClO41606.34776.4Al57122.6169722.6CaO26510.578910.5Total2521100.07497100.0

[0034]In each example, the raw materials were charged to a rotating drum mixer and homogenized until the reactants were uniformly dispersed throughout the entire charge.

[0035]The vacuum chamber system was divided in an interior vacuum vessel and an external surrounding chamber. The interior vacuum chamber vessel was protected with a refractory lining to prevent overheating and to support the reactor vessel. The external chambe...

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Abstract

Processes for producing low-nitrogen metallic chromium or chromium-containing alloys, which prevent the nitrogen in the surrounding atmosphere from being carried into the melt and being absorbed by the metallic chromium or chromium-containing alloy during the metallothermic reaction, include vacuum-degassing a thermite mixture comprising metal compounds and metallic reducing powders contained within a vacuum vessel, igniting the thermite mixture to effect reduction of the metal compounds within the vessel under reduced pressure i.e., below 1 bar, and conducting the entire reduction reaction in said vessel under reduced pressure, including solidification and cooling, to produce a final product with a nitrogen content below 10 ppm. The final products obtained, in addition to low-nitrogen metallic chromium in combination with other elements, can be used as raw materials in the manufacture of superalloys, stainless steel and other specialty steels whose final content of nitrogen is below 10 ppm.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to metallothermic processes for producing metallic chromium and its alloys. More specifically, the present invention relates to metallothermic processes for producing low-nitrogen metallic chromium and chromium-containing alloys and to the products obtained by said processes.[0003]2. Description of Related Art[0004]The lifespan of rotating metal parts in aircraft engines is typically determined by fatigue cracking. In this process, cracks are initiated at certain nucleation sites within the metal and propagate at a rate related to the material characteristics and the stress to which the component is subjected. That, in turn, limits the number of cycles the part will withstand during its service life.[0005]Clean melting production techniques developed for superalloys have given rise to the substantial elimination of oxide inclusions in such alloys to the extent that nowadays, fatigue cracks ...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): C22B34/32C22B5/04C22B9/04C22C27/06C22C19/05C22C1/04C22C1/06
CPCC22B34/32C22B5/04C22B9/04C22C27/06C22C1/06C22C19/05C22C1/045
InventorSERNIK, KLEBER A.VIERIA, ALAERCIO SALVADOR MARTINSRIOS, ADRIANO PORFIRIOFRIDMAN, DANIEL PALLOS
OwnerCIA BRASILEIRA DE METALURGIA E MINERCAO